PRECENDENCE CONSTRAINS VS CONDITIONAL SPLIT--CONFUSION WHEN TO USE

Precedence Constraints and Conditional Split are both components used in SQL Server Integration Services (SSIS) to control the flow of data and tasks within a package, but they serve different purposes and work in slightly different ways.

Precedence Constraints:

1. Purpose:
   

   • Precedence Constraints are used to define the logical flow of tasks and containers within a control flow.

1. Conditions:
   

   • Precedence Constraints are based on the success, failure, or completion status of preceding tasks or containers. They are not based on the content of the data.

1. Number of Paths:
   

   • Precedence Constraints typically lead to a binary decision: either a task runs or it doesn't, based on the outcome of the preceding task.

1. Execution Order:
   

   • Precedence Constraints dictate the order in which tasks and containers are executed within the control flow.

1. Usage Example:
   

   • You might use a Precedence Constraint to ensure that Task B only runs if Task A succeeds.

Conditional Split:

1. Purpose:
   

   • Conditional Split is a transformation within the Data Flow task that routes data rows to different outputs based on specified conditions.

1. Conditions:
   

   • Conditional Split evaluates conditions based on the content of the data rows. It routes data based on these conditions.

1. Number of Paths:
   

   • Conditional Split can route data to multiple outputs, allowing for more complex branching logic based on data content.

1. Execution Order:
   

   • Conditional Split operates within the Data Flow task and doesn't directly affect the execution order of tasks in the control flow.

1. Usage Example:
   

   • You might use a Conditional Split to separate incoming data into different streams based on criteria such as filtering by specific values, ranges, or other conditions.

Key Differences:

1. Control Flow vs. Data Flow:
   

   • Precedence Constraints operate within the Control Flow, controlling the execution order of tasks and containers. Conditional Split operates within the Data Flow, routing data based on conditions.

1. Conditions:
   

   • Precedence Constraints are based on the status (success/failure/completion) of tasks or containers. Conditional Split is based on conditions evaluated against data rows.

1. Number of Paths:
   

   • Precedence Constraints typically lead to a binary decision (run or don't run a task). Conditional Split can route data to multiple outputs, allowing for more complex branching based on data content.

1. Use Cases:
   

   • Precedence Constraints are used to sequence tasks and containers. Conditional Split is used to split data based on conditions.

In summary, Precedence Constraints control the flow of tasks in the control flow based on task outcomes, while Conditional Split is used to route data within the data flow based on conditions evaluated against the data itself.